The proposed work will develop lightweight multifunctional composite materials based on high hydrogen content polybenzoxazine (PBZ) composites that provide excellent radiation shielding capabilities as well as high strength, stiffness, and toughness. This approach provides a novel path to addressing NASA's need for lightweight radiation shielding materials that can also serve as structural members and provide protection from micrometeoroid impact. Polybenzoxazines are organic thermosetting polymers that can be tailored at the molecular level to optimize characteristics that are particularly advantageous for radiation shielding applications, such as high hydrogen content. Polybenzoxazines are also easily synthesized from inexpensive raw materials and the precursor, either monomeric or polymeric, can lead to cross-linked, lightweight, and thermally stable polymers. Our project will address the radiation shielding needs identified by NASA by developing lightweight composites containing a high hydrogen content polybenzoxazine resin matrix and ultra-high molecular weight polyethylene (UHMWPE) reinforcing fibers. UHMWPE fibers are the preferred reinforcing fiber for radiation shielding applications due to their high hydrogen content. Recent developments in PBZ chemistry now allow for crosslinking at lower temperatures that will not be detrimental to the polyethylene fiber structure.